Flecainide is an antiarrhythmic agent classified under subgroup 1C. It is a potent blocker of sodium and potassium channels with slow unblocking kinetics. While it is effective in treating certain types of arrhythmias, its use is associated with significant risks, including a potential increase in mortality. This article will explore the mechanism of action, risks, and therapeutic uses of flecainide.
Mechanism of Action
- Sodium and Potassium Channel Blockade: Flecainide effectively blocks both sodium and potassium channels, albeit with slow unblocking kinetics.
- No QT Interval Prolongation: Unlike some other antiarrhythmic agents, flecainide does not prolong the action potential or the QT interval.
- No Antimuscarinic Effects: Flecainide does not have antimuscarinic properties.
- Supraventricular Arrhythmias: Flecainide is used for patients with otherwise normal hearts who suffer from supraventricular arrhythmias.
- Premature Ventricular Contractions: The drug is very effective in suppressing premature ventricular contractions.
Risks and Limitations
- Exacerbation of Arrhythmia: Flecainide can severely exacerbate arrhythmias, even at normal doses, in patients with preexisting ventricular tachyarrhythmias and those with a history of myocardial infarction and ventricular ectopy.
- Increased Mortality: The Cardiac Arrhythmia Suppression Trial (CAST) was terminated prematurely due to a two and one-half-fold increase in mortality rate among patients receiving flecainide and similar group 1C drugs.
- Absorption and Half-Life: Flecainide is well absorbed and has a half-life of approximately 20 hours.
- Elimination: The drug is eliminated both by hepatic metabolism and by the kidneys.
- Dosage: The usual dosage of flecainide is 100–200 mg twice a day.
Flecainide is a potent antiarrhythmic agent with specific indications, particularly for treating supraventricular arrhythmias in patients with otherwise normal hearts. However, its use comes with significant risks, including the potential for exacerbating existing arrhythmias and increasing mortality. Therefore, flecainide should be used cautiously and under close medical supervision, taking into account its pharmacokinetics and the specific needs of the patient.